Conventionally a tap is rotated and moved linearly by a spindle motor for rotating the spindle and a Z-axis motor for moving the spindle linearly along an axis thereof, i.e., a direction Z. The spindle is rotated at a set speed corresponding to the pitch of a thread to be cut when a workpiece is tapped by a tap attached to the spindle of a machine tool. In this operation, the motors are affected by load fluctuations during the tapping process, depending on the output of each motor, and thus a thread having a constant pitch is not always formed. Therefore, an error of the pitch of the thread to be tapped is absorbed by a floating tapper tap system, i.e., a system wherein a spring is incorporated to force the tap along the axis of the spindle.
The above-mentioned floating tapper tap system, however, is not always suitable for high speed tapping with a high accuracy, and the products must be inspected for defects, and thus the production efficiency is lowered.